Laser-Induced Microstructural Modification of Polycrystalline Cu and Ag Films Encapsulated in SiO 2

Excimer-laser-induced rapid lateral solidification was used to produce large grain microstructures in copper and silver thin films. These were multilayer thin film structures consisting of sputter deposited copper and silver thin films encapsulated by silica (SiO2/metal/SiO2/Si substrate). In this process, a single excimer laser pulse and projection imaging optics were used to melt a 60 micron wide line in the metal film. The resolidification of the melted lines is found to occur laterally in the plane of the film, resulting in grains greater than 20 um in length and 1 um wide. Electron diffraction analysis allowed identification of a strong texture in the growth direction along the major axis of the elongated grains as well as similar texture parallel to the film surface. Various dislocation and faulted defect structures are identified and examined in the context of the rapid solidification and potential application to interconnects.